1. Field of the Invention
This invention relates to an assembly which allows a rotatable shaft to be centered on an axis with a high degree of precision. More particularly, it relates to such an assembly in which a rotatable shaft mounted in bearings is maintained centered on the axis despite wear of the bearings during use of the shaft. Most especially, it relates to such an assembly particularly adapted for use with a cutter of a high speed labeling machine.
2. Description of the Prior Art
High speed roll fed labeling systems are in widespread use in the packaging industry. For example, such a system is disclosed in the following commonly assigned issued patents: Hoffmann, U.S. Pat. No. 3,765,991, issued Oct. 16, 1973; Hoffmann, U.S. Pat. No. 3,834,963, issued Sept. 10, 1974; Hoffmann, U.S. Pat. No. 4,108,710, issued Aug. 22, 1978; Hoffmann, U.S. Pat. No. 4,108,711, issued Aug. 22, 1978 and Hoffmann, U.S. Pat. No. 4,500,386, issued Feb. 19, 1985. As disclosed, in this system, continuous, preprinted label stock is fed between a rotating cutter blade and a stationary cutter blade which is pivoted into its stationary position as the rotary blade moves past the stationary position. The label stock is cut as the two blades pass each other very closely. A second example of such a system is disclosed in commonly assigned Hoffmann, U.S. Pat. No. 4,181,555, issued Jan. 1, 1980 and Dickey, U.S. Pat. No. 4,188,843, issued Feb. 19, 1980. In this system, the continuous, preprinted label stock is fed between an anvil roller and a rotary cutter to sever the label stock into individual labels. Conventionally, the label stock is paper, a paper plastic lamination, a foil paper lamination and similar stiff materials.
More recently, there has been a demand for machinery capable of applying soft film labels. The soft film labels are fabricated from plastic materials that are usually less expensive and have more sparkle and sales appeal than the conventional stiff material labels. However, these soft film label materials have characteristics that make them difficult to handle on high speed roll fed machines. These difficulties arise from the limpness of the material and static charges which tend to reside on such labels. A major difficulty arises in cutting these soft materials with conventional equipment. Very close tolerances of the cutting equipment are required to cut these materials reliably at high speeds. In particular, a highly accurate distance and near zero clearance must be maintained between the rotary cutter blade and its associated pivotable, stationary cutter blade or anvil roller.
The shafts for the rotary cutter and the stationary cutter or anvil roller are rotatably supported in ball bearings or roller bearings and are adjusted to the required positions when the labeling system is installed. However, with wear of the bearings, the rotary cutter and stationary cutter or anvil roller become free to change their spacing with respect to one another. Some prior art cutter assemblies include the ability to adjust for bearing wear, but adjustment of such prior art assemblies requires a skilled technician and cannot be accomplished by a typical user of the labeling system.